1. Field of the Invention
The present invention relates to a lapping machine for lapping a row bar formed with a plurality of head elements arranged in a line, and a lapping method for lapping such a row bar.
2. Description of the Related Art
In a manufacturing process for a magnetic head slider, for example, a magnetic head thin film is formed on a substrate and next subjected to lapping, thereby making constant the heights of a magnetoresistive layer and a gap in the magnetic head thin film. The heights of the magnetoresistive layer and the gap are required to have an accuracy on the order of submicrons. Accordingly, a lapping machine for lapping a row bar as a workpiece is also required to have a high accuracy. Thus, the magnetic head slider is lapped so that the height of the magnetoresistive film becomes constant. However, the row bar is very thin, and its thickness is about 0.3 mm, for example.
Accordingly, it is difficult to lap the row bar directly by the lapping machine, and the row bar is therefore bonded to a row tool before lapping. That is, the row bar bonded to the row tool is pressed on a lap plate during lapping. As known from U.S. Pat. No. 5,023,991 and Japanese Patent Laid-open. No. Hei 5-123960, for example, the resistances of electrical lapping guide elements (ELG elements) formed integrally with the row bar are always measured during lapping. Then, whether or not the height of the magnetoresistive film of each magnetic head element has become a target height is detected according to the measured resistance of each ELG element. When it is detected that the magnetoresistive film has been lapped up to the target height, according to the measured resistance, the lapping operation is stopped.
Thereafter, the lapped surface of the row bar is formed into the shapes of flying surfaces of a plurality of magnetic head sliders, and the row bar is next cut into the plurality of magnetic head sliders in the condition that it is bonded to the row tool. Thereafter, the row tool is heated to melt an adhesive bonding the row bar to the row tool, thereby removing the magnetic head sliders from the row tool to obtain the individual magnetic head sliders. In this manner, a wafer is cut into a plurality of row bars each having the plural magnetic head elements arranged in a line, and each row bar is subjected to lapping by using the row tool. Accordingly, the magnetoresistive films of the plural magnetic head elements can be lapped at a time.
However, there are variations in height among the magnetoresistive films of the plural magnetic head elements in the row bar on the order of submicrons, depending on the accuracy of film deposition of the magnetoresistive films, the accuracy of bonding of the row bar to the row tool, etc. It is accordingly necessary to correct for such variations in the lapping operation for mass production of magnetic head sliders uniform in characteristics. There have been proposed various conventional methods for correcting for the above-mentioned variations on the order of submicrons in the lapping operation. For example, U.S. Pat. No. 5,607,346 has proposed a method such that a plurality of holes are formed through the row tool and forces are applied from actuators through these holes to the row tool.
However, these actuators are required to have capacities of applying relatively large forces to these holes, in order to obtain a desired pressure distribution, and it is therefore difficult to manufacture such actuators acting on a plurality of load points. As a result, the spacing between any adjacent ones of the plural load points (the plural holes) cannot be greatly reduced, causing a difficulty of improvement in lapping accuracy.
It is therefore an object of the present invention to provide a lapping machine and a lapping method which can improve the accuracy of lapping of a row bar formed with a plurality of head elements arranged in a line.
In accordance with an aspect of the present invention, there is provided a lapping machine for lapping a row bar formed with a plurality of head elements arranged in a line, comprising a lap plate for providing a lapping surface; a row tool having a plurality of bend cells formed by defining a plurality of slits; a pressure mechanism for pressing the row tool toward the lapping surface of the lap plate; and a bend mechanism for bending the bend cells of the row tool toward the lapping surface of the lap plate; the bend mechanism comprising an air cylinder unit having a plurality of double-acting air cylinders; a plurality of racks operatively connected to the double-acting air cylinders, respectively; a plurality of first pinions arranged coaxially and meshing with the racks, respectively, each of the first pinions being integrally formed with a lever; a plurality of second pinions arranged coaxially and meshing with the racks, respectively, the second pinions being spaced apart from the first pinions; and a guide mechanism for guiding each of the racks, the respective first pinion, and the respective second pinion in substantially the same plane; each of the bend cells of the row tool having an engaging hole for engaging a front end of each lever, whereby each lever engaged with the engaging hole is rotated to bend each bend cell of the row tool toward the lapping surface of the lap plate.
Preferably, the bend mechanism further comprises a plurality of electro-pneumatic conversion regulators connected to the double-acting air cylinders, respectively; and a compressed air source connected to the electro-pneumatic conversion regulators. Preferably, the row tool further has first and second ends between which the bend cells are formed; a pair of fixed cells formed at the first and second ends, each of the fixed cells having a width larger than that of each bend cell; and a parallel spring mechanism formed by defining a through hole extending from the first end to the second end.
Preferably, the guide mechanism comprises a rack guide having a plurality of guide gaps for guiding the racks, respectively; each of the racks has a first surface formed with a gear and a second surface formed with a projection opposite to the first surface, the projection being in contact with the rack guide; and each of the racks is supported at a first point of contact with the respective first pinion, a second point of contact with the respective second pinion, and a third point of contact with the rack guide at the projection, whereby each rack is linearly reciprocated in a horizontal direction.
In accordance with another aspect of the present invention, there is provided a bend mechanism for locally bending a row bar formed with a plurality of head elements arranged in a line, comprising a plurality of racks arranged in a direction perpendicular to a direction of movement of the racks; and a plurality of first pinions arranged coaxially and meshing with the racks, respectively, each of the first pinions being integrally formed with a lever.
Preferably, the bend mechanism further comprises an air cylinder unit having a plurality of double-acting air cylinders, each of the double-acting air cylinders having a piston and a piston rod connected to the piston; a plurality of second pinions arranged coaxially and meshing with the racks, respectively, the second pinions being spaced apart from the first pinions; and a guide mechanism for guiding each of the racks, the respective first pinion, and the respective second pinion in substantially the same plane; the racks being connected to the piston rods of the double-acting air cylinders, respectively.
Preferably, the guide mechanism comprises a rack guide having a plurality of first guide gaps, and a pinion guide having a plurality of second guide gaps; the racks being guided in the first guide gaps of the rack guide, respectively; the first and second pinions being guided in the second guide gaps of the pinion guide, respectively.
In accordance with a further aspect of the present invention, there is provided a lapping method for lapping a row bar formed with a plurality of head elements arranged in a line, comprising the steps of providing a lapping surface by a lap plate; bonding the row bar to a lower surface of a row tool having a plurality of bend cells formed by defining a plurality of slits; pressing the row bar on the lapping surface; and operating a bend mechanism including an air cylinder unit having a plurality of double-acting air cylinders, a plurality of racks operatively connected to the double-acting air cylinders, respectively, and a plurality of pinions arranged coaxially and meshing with the racks, respectively, each of the pinions being integrally formed with a lever, thereby applying an adjustable bending pressure to each of the bend cells; whereby the row bar is bent at a plurality of points to perform lapping of the row bar.
In accordance with a still further aspect of the present invention, there is provided a row tool to which a row bar formed with a plurality of head elements arranged in a line is to be bonded, comprising a plurality of bend cells formed by defining a plurality of slits, each of the bend cells having an engaging hole; first and second ends between which the bend cells are formed; a pair of fixed cells formed at the first and second ends, each of the fixed cells having a width larger than that of each bend cell; and a parallel spring mechanism formed by defining a through hole extending from the first end to the second end.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.